People have realized how important the environment is, but still trees ____in the world every year.— We must do something to stop it.

re were no exams and parents meetings, highschool life __ much enjoyable.

I’d rather you did some housework when you are free ,but you .

Tsinghua University,________ in 1911,is home to a great number of outstanding figures.

I think our company lays too much ______ oncost and not enough on quality.